Delay electric initiators



De 9, 1958 R. Ajw. HILL ETAL 2,863,392

DELAY ELECTRIC INITIAToRs Filed July 18, 195s 2,863,392 Patented Dec. 9,1958 DELAY ELECTRIC INITIAToRs Royston Arthur Walter Hill and RobertWalter Moody, West Kilhride, Scotland, assignors to Imperial ChemicalIndustries Limited, London, England, a corporation of Great BritainApplication July 18, 1956, Serial No. 598,584

Claims priority, application Great Britain August 15, 1955 7 Claims.(Cl. 102-28) It has now been found that by using for the delay elep menta metal tube having its lower end closed and containing a small quantityof a primary explosive composition Ibetween the closed end of the metaltube and the lower end of the column of delay composition it is possibleto provide delay detonators which are non-incendiary and which have ahigh degree of regularity over wide ranges of delay times as forinstance delay periods ranging from 20 milliseconds to 5 seconds.

According to the present invention a ventless delay electric deto-natorlcomprising a casing of copper, zinc, copper alloy or zinc alloycontaining therein a base charge of a secondary explosive compositionand a superimposed charge of a primary explosive composition and havinga delay element consisting of a metal tube containing therein a delayfuse composition and interposed between the primary explosivecomposition and an electric fusehead is characterised in that the lowerend of the metal tube is closed and contains a small charge of a primaryexplosive composition between the closed end thereof and the lower endof the column of delay fuse composition and in that said delay elementis so secured in the casing that it is retained on the firing of thedetonator.

Said metal tube of the delay element may be of copper alloy or of mildsteel but not of aluminium and it must not be deformed to anysubstantial degree during the loading of the delay composition thereinand must not disintegrate on the tiring of the detonator.

The delay element is retained in the casing on explosion of thedetonator by for example crimping the casing to the metal tube of thedelay element or preferably by having an intervening metal tube of forinstance copper, copper alloy, mild steel, zinc or zinc alloy betweenthe delay element and the casing and crimped to the casing. Thisintervening metal tube is preferably provided with a small aperture inits lbase of smaller diameter than the inner diameter of the metal tubeof the delay element. Furthermore the metal tube of the delay elementshould preferably t tightly in this intervening metal tube.

The diameter, nature and amount of the delay fuse composition in themetal tube of the delay element can be those normally characteristic fordelay elements in delay electric detonators. For instance the diameterof the delay fuse composition in the metal tube of the delay element maybe 3.3 mm., the length of the column of the delay composition may varyfor example between 3 and 30 mm., and the delay fuse composition may befor instance a substantially gasless mixture of oxidising agents andreducing agents for example one consisting of lead dioxide and siliconor potassium permanganate and antimony.

AThe del-ay element should preferably be in contact with the uppersurface of the primary explosive composition in the casing so that theshock wave for-med on the detonation of the primary explosivecomposition in the metal tube of the delay element is transmittedthrough the bottom of this metal tube and readily initiates theexplosion of the primary explosive composition in the casing. As themetal tube of the delay element does not disintegrate but remains intacton the firing of the detonator no hot particles of slag from the delaycomposition or from the fusehead are ejected on the firing of thedetonator and so the danger of ignition of inllammable methane/'airmixtures is removed.

On examination of the delay detonators according to the invention aftertheir ring it is found that although the base of the casing is blownaway the metal tube of the delay element remains in position within thecasing and that the slag for-med is retained within the casing.Furthermore it has also been experimentally conrmed that hot(luminescent) 4particles are not ejected from the detonators of theinventiony 'when they are red by comparing photographs of the streams ofthe particles issuing from these detonators when they are tired withthose of the streams of the particles issuing from instantaneous copperdetona'tors and normal short delay copper detonators when these arefired.

The invention is illustrated by way of example with reference to thediagrammatic drawings accompanying the specification in which 1 is acopper tube, 2 is a base charge, 3 is a superimposed primary charge, 4is a copper tube which contacts the charge 3 and is provided with a hole5, 6 is a-mild steel tube having its lower end closed and containing aninitiating charge 7 on top of which is a column 8 of delay fusecomposition, 9 is an electric fusehead and 10 is a neoprene plug towhich the tubes 1 and 4 are crimped and through which pass the leadingwires 11 for the electric fusehead 9.

The invention is further illustrated by the following examples.

Example 1 -For a delay detonator of mean delay time of 266 millisecondscopper tube 1 is of an external diameter 7.14 mm. and a length of 65mm., base charge 2 is 0.25 gram tetryl, primary explosive charge 3 is0.35 gram of an aluminium/lead azide/lead styphnate composition, coppertube 4 is of an external diameter 6.52 mm. and a length 52 mm., hole 5is of a diameter 1.90 mm., mild steel tube 6 is of an external diameter6.02 mm. and internal diameter 3.30 mm., a length 21.5 mm. and a basethickness 0.76 mm., the initiating charge 7 consists of 0.03 gram leadazide and the delay fuse composition 8 consists of lead dioxide/silicon(S0/50) pressed at 18 tons per square inch.

In order to test for instance 25 of these detonators for gas ignitioneach detonator is suspended in a 9% (by volume) methane/methane airmixture and is tired by a single shot exploder and it is found that nota single detonator ignites the methane air mixture. Each of for instance30 of these detonators is also tired to determine scatter and it isfound that the scatter is 3l milliseconds.

Example 2 Fora delay detonator of mean delay time of 2.26 seconds thedimensions and compositions are the same asin Example. l .except thatmetal `tube 6' is .of a. length 13.0 mm. and the delay fuse composition8 consists of potassium permanganate/antimony (36/ 36).

. In order to test for instance, .l'Onof these detonators for Example 3For a delay detonator of mean delay time of 27 milliseconds thedimensions and compositions are the same as in Example l except thatythe metal tube 6 is of a length mm.

In order to test for instance 25 of these detonators for gas ignitioneach detonator is suspended in a 9% (by Volume) methane/methane airmixture and is fired by a single shot exploder and it is found. that nota single detonator ignites the methane air mixture. Each of for instance25 of these detonators is also tired to determine scatter and it isfound that theV scatter is 8 milliseconds.

What We claim is:

l. A ventless delay electric detonator comprising 'a metallic casingcontaining therein a fusehead, a base charge of a secondary explosivecomposition and a superimposed vcharge of a primary explosivecomposition and having a delay element including a metal tube containingtherein a delay fuse composition, said delay element be- Y inginterposed between said primary explosive composition and said fusehead,said delay fuse composition beingv of the gasless type and said'metaltube having its lower end nonrupturably sealed against thereaction of its contents and secured so as to be retained in thedetonator casing on firing of the detonator, and a small charge ofprimary explosive composition being disposed within said metal tubebetween the gasless delay composition and the .closed end of the tube.

2. A ventless delay electric detonator as claimed in claim 1 whereinsaid metal tube is formed of a material selected from the groupconsisting of a copper alloy and mild steel.

V3. A ventless electric detonator according to claim l wherein saidcasing is crimped to said metal tube.

4. A ventless electric delay detonator comprising a metallic casing, abase charge of a secondary explosive, a superimposed charge of a primaryexplosive composition and a fusehead in said casing, a delay element insaid casing comprising a metal tube containing therein a delay fusecomposition and interposed between said primary explosive compositionand said fusehead, said delay composition being of the gasless type andsaid metal tube having its lower end nonrupturably sealed against thereaction of its contained constituents, a small quantity of a primaryexplosive composition disposed `Within said tube between lthe delaycomposition yand the closed end of said tube and an intervening secondmetal tube between said casing and said delay element tube, said secondtube being assembled to retain the delay element tube Within thedetonator-casing upon firing of the detonator.

A 5. A ventless electric detonator as claimed in claim 4 wherein said'second metal tube has a basal aperture of smaller diameter than that ofthe interior of said delay element metal tube.

6. A ventless electric detonator as claimed in claim 4 wherein saidgasless delay fuse composition is a substantially gasless mixture oflead dioxide and silicon.

7. A ventless electric detonator as claimed in claim 4 wherein saidgasless delay fuse composition is a substantially gasless mixture ofpotassium permanganate and antimony.

References Cited in the file of this patent UNITED STATES PATENTSAustralia May 2l,

